Well scoubidou I do this:
Get the wing area let say 1150 and divide it by 144
1150/144=7.99
Then get the weight let say 15 lbs and multiply it by 16,
this will change the weight to oz
15x16=240 oz
And finally divede the weight result by the wing area result
240/7.99=30.04

30.04 will be the wing loading for that amount of wing area and weight.
Remember the lower wing loading the better

This way I know the max weight the aircraft should have to
fly light, to be in the good range or to be to heavy.
Hope this help
Benny